[the_gentlegiant]

Greetings All,

I posted this, ahem, on another forum, but have yet to receive any help. Hoping the folks over here have more knowledge of things.

I'll stick to the basics.

Mid 90's Mori SV-50 VMC pallet changer. Ground up rebuild. Fanuc 18C control. With the machine exactly where I wanted its home positions to be, I've reset all home positions using P-Cancel and changing parameter 1815.4 to 1 and so on. Important: No deceleration, but hard over travel dogs only. Software limits. (Stored Stroke Check.) How do I zero return with existing and probably useless grid shift numbers, but still end up exactly where I want to be without crashing into anything in the process? Safe to crash margin is 5mm or less. Even though the machine uses absolute encoders, at some point this machine will need a zero return. It just will. As with this and most machines... there are even bulbs or LED's just waiting to be turned on by a Zero Return.

Current gridshift parameters are as follows: N1850 A1 P-12590 A2 P-7280 A3 P 4200 A4 P 0

It would be my guess, and also my doubt, that these numbers had anything to do with me changing parameter 1815.4 from 0 to 1. Should I now do a zero return, I can't imagine how they wouldn't pay it forward, and potentially try to run me past the stops.

My only thought is to zero out the shifts, run zero return, and calculate the shift needed to get where I'm going. I have taped the rails to mark where the bearing trucks should stop. I'm a little nervous about what a negative grid shift number means in reality. Wipes out my tape marks, or falls short? I'd prefer not to find out by trial and error. Please help if you can. Thank you.

For those knowledgeable of the SV-50 and 18C control, I have a few more questions for the future if you'd be so inclined to help. Many thanks in advance.

David

[STLMachinist]

Change 1815.4=0 and 1850=0 for all axes, cycle power. Then use the handle to move all axes to where you want the home position, then set 1815.4=1. This should set wherever the axes are at to home position.

[the_gentlegiant]

Hi STL,

As my post says, I've already done that, but I believe there is no way for the encoders to bring the machine exactly back to that position using the "Zero Return" function. The grid numbers in the control did not change from what they were before cycling parameter 1815.4. Zero Return uses grid shift functionality. While putting the machine back together, there is no chance that the index marker on any encoder was set back to exactly the same place it was before. I'm just going to make sure my hard over-travels are set correctly and try Zero Returning one axis. Maybe I'll learn what I need to do from what happens there.

[STLMachinist]

... I'm confused. If you set 1815.4, wherever the axis is at is now it's new home position. If you use the zero return function it should go back to that exact spot everytime. That's what the zero return function does. It brings it to the reference/home position which is set by 1815. Grid shift parameters never change automatically. Your soft OT's are based off your home positions.

[the_gentlegiant]

Turns out I was perhaps over cautious. I made sure all my soft and hard stops were set properly. Put the axis only about an inch from home, and pressed Zero Return. No problems... just went right to where it was supposed to go. I guess I'll always wonder how grid shift works in a machine without deceleration dogs to start the gridshift counting. Maybe the non-decel machines just do some math off of the soft limits.

Regardless... machine is all homed in. Thanks.